The invention is based on a magnetic valve for a fluid-controlled heating and/or cooling installation.
Such magnetic valves are used particularly in fluid-controlled heat exchangers for heating and/or air conditioning systems of motor vehicles. They can be triggered in clocked fashion as a function of the temperatures in the kg or in a passenger compartment, and the flow is determined substantially by the mean time cross section. By means of the fluid pressure and/or a valve spring, the valve member of the magnetic valve is opened, and it is closed by an excited coil of the magnetic valve by acting on an armature connected to the valve shaft. The chamber in which the armature is disposed is not hermetically sealed but instead is filled with fluid. This is intended to damp the motion of the armature hydraulically, in order to avert an abrupt closure and attendant pressure surges in the fluid system. This also prevents both noise and wear that occur when the valve member strikes the valve seat without damping. The damping action is severely impaired, however, by gas and particularly air bubbles that collect in the armature chamber, for instance when the system is filled. The magnetic valves can also be used as reversing valves, which short-circuit the coolant flow from the internal combustion engine in a first switching position and in a second switching position cause it to flow via a heat exchanger.
From German Patent DE 195 370 67 C1, in a magnetic valve disposed in a forward flow line of a heat exchanger of a heating system, it is known, by using the pressure drop between the forward flow line and the return line, to cause a flow through the armature chamber of the magnetic valve, in order to remove the air bubbles from the armature chamber and to avert the attendant disadvantages. To that end, a venting line is provided between the armature chamber and the return line, while by way of an annular gap between the armature and the coil of the magnetic valve, fluid from a forward flow line flows into the venting line and prevents air bubbles from collecting in the armature chamber.
From German Patent DE 34 164 65, in a magnetic valve, it is also known to connect an armature chamber to a line segment located on the side of the valve member toward the armature chamber by way of an axial conduit in an armature shaft. The pumping action of the armature during the valve actuation is intended to positively displace air from the armature chamber and to aspirate fluid. Because of the compressibility of the air, however, a sufficient exchange of fluid does not always take place between the armature chamber and the line segment, and under some circumstances the air can remain trapped in the upper, annular portion of the armature chamber.
The valve member is guided axially limitedly displaceably in the valve shaft. By means of the fluid pressure, it is pressed in the opening position against a stop on the valve shaft. If the coil of the magnetic valve is excited, then the armature secured to the valve shaft is attracted, and the valve shaft presses the valve member against a valve seat. If the valve member strikes the valve seat undamped, it causes noise because of the impulse of the impact and increases wear.